The determination of the wave form of alternating currents without a contact maker
Harris J. Ryan · Transactions of the American Institute of Electrical Engineers · 1899
A methodis given in this paper for determining the wave forms of alternating currents which uses no highly specialized measuring apparatus. No contact maker is used, and it is generally appliable on polyphase circuits only. It is recommended as a method which may be used under many circumstances where the special contact maker apparatus is not available.